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Re: isa strangeness

From: Jaroslav Hajek
Subject: Re: isa strangeness
Date: Mon, 16 Aug 2010 09:02:19 +0200

On Mon, Aug 16, 2010 at 8:50 AM, Martin Helm <address@hidden> wrote:
> Am Montag, 16. August 2010, 08:10:47 schrieb Jaroslav Hajek:
>> On Mon, Aug 16, 2010 at 4:31 AM, Martin Helm <address@hidden> wrote:
>> > The help string of isa is not really good here.
>> > Use
>> > isa(10, "double") or isa(10, 'double')
>> > class in isa is expected to be a string here which contains the class
>> > name. The reason is the syntax
>> > isa(10, double)
>> > will treat double as a function call without arguments, which is a syntax
>> > error.
>> > - mh
>> On the contrary, I think that the help string is OK, It's just that
>> Richard doesn't understand the fundamentals of Octave syntax; but we
>> surely can't repeat those in every docstring, can we?
> I try to think like someone who  never  has used octave or matlab here (and I
> think he mentioned that in an indirect way by stating that he installed
> yesterday octave and works through the manual).

Yes, most likely that's why he doesn't understand. I wasn't implying
anything about Richard's mental capabilities or whatever else.

> And if I read the output of "help isa" it is not clear (for me it was , but
> probably simply because I am used to it and never think about that) that CLASS
> is a name (in fact looking at the code with "type isa" the same input variable
> is called cname in the code which is much more descriptive).

What else can CLASS be? The example Richard tried

isa (10, double)

makes no sense because an unquoted non-keyword plain literal in Octave
implies either a variable query or, if no such variable exists, a
function/class call. *CALL*, not reference. It's obvious that you
don't want a call here.
The next example

isa (10, double(10))

makes even less sense. Only the final one was correct, albeit not
useful. I still think the docstring is OK, although you're welcome to
improve it. Octave simply treats name somewhat differently than, say,
Python, but once you learn how, it makes sense.


RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic

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